The explicit expression of Eq. (REF ) accounting for the correct numeric coefficients at one-loop order is [1]}, [2]}
\({\cal L}_{\rm int}/m_e^4\simeq \frac{1}{360\pi ^2}\Bigl (\frac{e}{m_e^2}\Bigr )^4\Bigl (4{\cal F}^2+7{\cal G}^2\Bigr )\,.\) 
